Marijuana By Itself Not a Significant Factor in Fatal and Injury Crashes in 2012, DPS Data Shows

Pot by itself was not much of a factor in injury and fatal crashes probed last year by the Arizona Department of Public Safety.

Fewer than 1 percent of suspected impaired drivers involved in such crashes tested positive for nothing but marijuana.

New Times' findings, based on a records request satisfied by DPS this week, jibe with statistics we reported earlier this month in our feature article about Arizona's zero-tolerance marijuana-DUI law (link below). Drivers suspected of impairment in crashes that hurt or killed people in Phoenix, Chandler, and Scottsdale were rarely found to be impaired by marijuana, our earlier research showed.

Alcohol is believed responsible for five to 10 times the number of crashes caused by drivers impaired by all other illegal drugs combined, according to the annual "Crash Facts" report put out by the Arizona Department of Transportation.

With medicinal herb now legal under state law for more than 37,000 people, we figured we'd find out what fraction of those drug cases involved pot. Not many, it turns out.

The concern seems rational. But data from the observations of state troopers and police don't seem to support fear of a looming disaster on the roadways.

In 2012, blood and urine tests ordered by DPS crash investigators prove that alcohol was the culprit in the vast majority of the 335 injury and fatal crashes involving impaired drivers.

Lab tests showed that only three of the 335 suspected impaired drivers had marijuana and nothing else in their bloodstreams.

(Quick caveat before we dump our numbers on you: Gleaned from the lab reports, they mix injury and fatal crashes -- we didn't see the entire crash reports -- just the drug and alcohol test results. The numbers don't include the fatal crashes in which the suspected impaired driver died. We omitted one report because, confusingly, it showed two suspects. In about 10 cases, two BAC readings were given, possibly taken from the suspect at different times -- we always picked the higher one.)

Here's what we found:

* 335 -- total suspected impaired drivers. These are the folks busted by DPS statewide in 2012 for suspected impaired driving after an injury or fatal crash, and for which tests for drugs, alcohol or both were performed.

* 3 -- THC or THC metabolite only. The inert carboxy-THC metabolite, which can remain in the bodies of some users for weeks, was found in all three cases, at nanogram-per-milliliter levels of three, 39 and 42. The suspect with the 42 ngs of carboxy was also reported to have 2 ng/ml of active THC. The new legalization law in Washington sets an active THC limit of 5 ng/ml for drivers -- the same amount approved recently by Colorado lawmakers but not yet signed into law by Governor John Hickenlooper.

* 285 -- alcohol-only cases. If the observed level of impairment matches the BAC shown in a breath test, police don't typically order a more expensive blood test. It's a safe bet that some of those 285 drunk drivers also had drugs or drug metabolites in their bloodstreams, including pot.

* .173 -- average BAC of the alcohol-only cases. That's about halfway between an extreme and a super-extreme DUI in Arizona. Nothing higher than .382 and with a low of .01.